1. Field of the Invention
The invention relates to novel open- and/or closed-cell elastomeric foams, and to a method for the production thereof.
2. Description of the Prior Art
It is known that polyurethane elastomers may be processed from polyols, 1,5-naphthylene diisocyanate, cross-linking agents, for example water, and/or expanding agents, into highly resilient elastomeric foams which can withstand impact loads, with compressions of up to 80%, without damage. For this reason, elastomeric foams of this kind, which can absorb heavy dynamic loads, are used in the construction of automotive vehicles, for example for impact-absorbers (mainly elastomeric foams of the Vulkollan (trade name) types).
It is also known that prepolymers made from polytetrahydrofuranepolyols, or mixtures thereof, and polyisocyanates, can be processed, in the presence or absence of catalysts and expanding agents with chain-lengthening agents, preferably polyamines (e.g. Moca.RTM. and Caytur/7.RTM.), into elastomeric foams (of the Adiprene.RTM. types).
Whereas elastomeric foams of the Vulkollan types absorb excessive amount of water, have low resistance to cold and hydrolysis, and must remain for relatively long periods of time in closed molds, elastomeric foams of the Adiprene.RTM. types have inadequate resistance to oxygen and ozone and the polyamine chain-lengthening agents contained therein are toxic. Moreover, it is difficult to control their specific weight and cell-structure solely by means of expanding agents which vaporize or decompose under heat and which, because of their necessarily low decomposition point (&lt;100.degree. C.), are explosive and, moreover, can be used only in the form of suspensions. Now if it is attempted, by reaction with isocyanate and water, to obtain carbon-dioxide as an additional expanding gas, this produces, in this system, hard segments, built up in various ways in the polymer matrix, which interfere with the highly distance-sensitive hydrogen-bridge formation in the hard segment, and this leads to a rapid decline in the levels of physical values.